bims-mitmed Biomed News
on Mitochondrial medicine
Issue of 2023–09–03
twenty-six papers selected by
Dario Brunetti, Fondazione IRCCS Istituto Neurologico
  1. The mitochondrial tRNA MT-TW m.5537_5538insT variant presents with significant intra-familial clinical variability.
  2. Mutation on MT-CO2 gene induces mitochondrial disease associated with neurodegeneration and intracerebral iron accumulation (NBIA).
  3. Mitochondrial dysfunction characterized in human induced pluripotent stem cell disease models in MELAS syndrome: A brief summary.
  4. Complex I deficiency in m.3243A>G fibroblasts is alleviated by reducing NADH accumulation.
  5. Preserved respiratory chain capacity and physiology in mice with profoundly reduced levels of mitochondrial respirasomes.
  6. Mitochondrial phospholipid metabolism in health and disease.
  7. Impaired age-associated mitochondrial translation is mitigated by exercise and PGC-1α.
  8. T cell differentiation drives the negative selection of pathogenic mitochondrial DNA variants.
  9. Resistance Exercise Training Rescues Mitochondrial Dysfunction in Skeletal Muscle of Patients with Myotonic Dystrophy Type 1.
  10. AMPK-FOXO-IP3R signaling pathway mediates neurological and developmental defects caused by mitochondrial DNA mutations.
  11. Expanding the spectrum of neonatal-onset AIFM1-associated disorders.
  12. Mitochondrial DNA mutations can influence the post-implantation development of human mosaic embryos.
  13. Beyond the TCA cycle: new insights into mitochondrial calcium regulation of oxidative phosphorylation.
  14. A defect in mitochondrial fatty acid synthesis impairs iron metabolism and causes elevated ceramide levels.
  15. Urolithin A as a Potential Agent for Prevention of Age-Related Disease: A Scoping Review.
  16. AAV-based in vivo gene therapy for neurological disorders.
  17. Previously unknown pathway for lipid biosynthesis discovered.
  18. Phage-assisted evolution and protein engineering yield compact, efficient prime editors.
  19. Targeting Duchenne muscular dystrophy by skipping DMD exon 45 with base editors.
  20. Friedreich's Ataxia-Health Index: Development and Validation of a Novel Disease-Specific Patient-Reported Outcome Measure.
  21. Patient and caregiver experiences with pantothenate kinase-associated neurodegeneration (PKAN): results from a patient community survey.
  22. Ataxia due to a COQ8A Novel Variant in Primary Coenzyme Q10 Deficiency.
  23. Cornelia de Lange Syndrome mutations in SMC1A cause cohesion defects in yeast.
  24. Boosting the efficacy of emergency contraception.
  25. The translational potential of cholesterol-based therapies for neurological disease.
  26. PINK1, Keap1, and Rtnl1 regulate selective clearance of endoplasmic reticulum during development.
  1. Am J Med Genet A. 2023 Aug 31.
    The mitochondrial tRNA MT-TW m.5537_5538insT variant presents with significant intra-familial clinical variability.
    Lauren Strasser, Asif Doja, Jorge Davila, Pranesh Chakraborty, Danielle K Bourque.
      Mitochondrial disorders can present with a wide range of clinical and biochemical phenotypes. Mitochondrial DNA variants may be influenced by factors such as degree of heteroplasmy and tissue distribution. We present a four-generation family in which 10 individuals carry a pathogenic mitochondrial variant (m.5537_5538insT, MT-TW gene) with differing levels of heteroplasmy and clinical features. This genetic variant has been documented in two prior reports, both in individuals with Leigh syndrome. In the current family, three individuals have severe mitochondrial symptoms including Leigh syndrome (patient 1, 100% in blood), MELAS (patient 2, 97% heteroplasmy in muscle), and MELAS-like syndrome (patient 3, 50% heteroplasmy in blood and 100% in urine). Two individuals have mild mitochondrial symptoms (patient 4, 50% in blood and 67% in urine and patient 5, 50% heteroplasmy in blood and 30% in urine). We observe that this variant is associated with multiple mitochondrial presentations and phenotypes, including MELAS syndrome for which this variant has not previously been reported. We also demonstrate that the level of heteroplasmy of the mitochondrial DNA variant correlates with the severity of clinical presentation; however, not with the specific mitochondrial syndrome.
    Keywords:  Leigh syndrome; heteroplasmy; lactic acidosis; mitochondrial disorders; mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS); phenotypic variability
    DOI:  https://doi.org/10.1002/ajmg.a.63378
  2. Biochim Biophys Acta Mol Basis Dis. 2023 Aug 26. pii: S0925-4439(23)00222-3. [Epub ahead of print] 166856
    Mutation on MT-CO2 gene induces mitochondrial disease associated with neurodegeneration and intracerebral iron accumulation (NBIA).
    Sarah Courtois, Chloé Angelini, Christelle M Durand, Nivea Dias Amoedo, Armelle Courreges, Elodie Dumon, Mégane Le Quang, Cyril Goizet, Marie-Laure Martin-Negrier, Rodrigue Rossignol, Didier Lacombe, Isabelle Coupry, Aurélien Trimouille.
      Mitochondrial diseases are genetic disorders impairing mitochondrial functions. Here we describe a patient with a neurodegenerative condition associated with myopia, bilateral sensorineural hearing loss and motor disorders. Brain MRIs showed major cortico-subcortical and infra-tentorial atrophies, as well as intracerebral iron accumulation and central calcifications, compatible with a NBIA-like phenotype. Mitochondrial DNA analysis revealed an undescribed variant: m.8091G>A in the MT-CO2 gene, associated with a complex IV deficiency and a decrease of the mitochondrial respiratory chain capabilities. We report here this pathogenic variant, associated with a NBIA-like phenotype.
    Keywords:  Complex IV; MT-CO2; Mitochondriopathies; NBIA; iron accumulation
    DOI:  https://doi.org/10.1016/j.bbadis.2023.166856
  3. Mitochondrion. 2023 Aug 25. pii: S1567-7249(23)00071-5. [Epub ahead of print]72 102-105
    Mitochondrial dysfunction characterized in human induced pluripotent stem cell disease models in MELAS syndrome: A brief summary.
    Kumarie Latchman, Mario Saporta, Carlos T Moraes.
      Human induced pluripotent stem cells (hiPSCs) for MELAS syndrome (mitochondrial myopathy, encephalopathy, lactic acidosis, stroke-like episodes) may allow deeper understanding of how tissue-specific mitochondrial dysfunction result in multi-systemic disease. Here, we summarize how the m.3243G mtDNA mutation affects mitochondrial function in different tissues using iPSC and iPSC-differentiated cell type disease models and what significant findings have been replicated in the independent studies. Through this brief review and with a focus on mitochondrial dysfunction in iPSC-differentiated cell types, namely fibroblast, neuron, and retinal pigment epithelium cells, we aim to bring awareness of hiPSC as a robust mitochondrial disease model even if many unanswered questions remain.
    DOI:  https://doi.org/10.1016/j.mito.2023.08.003
  4. Front Physiol. 2023 ;14 1164287
    Complex I deficiency in m.3243A>G fibroblasts is alleviated by reducing NADH accumulation.
    Tongling Liufu, Haiyan Yu, Jiaxi Yu, Meng Yu, Yue Tian, Yichun Ou, Jianwen Deng, Guogang Xing, Zhaoxia Wang.
      Introduction: Mitochondrial disease is a spectrum of debilitating disorders caused by mutations in the mitochondrial DNA (mtDNA) or nuclear DNA that compromises the respiratory chain. Mitochondrial 3243A>G (m.3243 A>G) is the most common mutation showing great heterogeneity in phenotype. Previous studies have indicated that NADH: ubiquinone oxidoreductase (complex I) deficiency accompanied by a decreased nicotinamide adenine dinucleotide (NAD+)/reduced NAD+ (NADH) ratio may play a pivotal role in the pathogenesis of m.3243A>G mutation. Methods: To evaluate the potential effects of strategies targeting the imbalanced NAD+/NADH ratio in m.3243A>G mutation, we treated fibroblasts derived from patients with the m.3243 A>G mutation using nicotinamide riboside (NR) or mitochondria-targeted H2O-forming NADH oxidase (mitoLbNOX). Results: M.3243 A>G fibroblasts showed a significant reduction in complex I core subunit 6, complex I enzymatic activity, complex I-dependent oxygen consumption rate (OCR), and adenosine triphosphate (ATP) production compared to the controls. The NAD+/NADH ratio was also significantly reduced in m.3243 A>G fibroblasts, and, using fluorescence lifetime imaging microscopy, we also found that the NADH level was elevated in m.3243 A>G fibroblasts. After NR treatment, the NAD+/NADH ratio, complex I-dependent OCR, and ATP levels increased, whereas NADH levels remained unchanged. More excitingly, after treatment with mitoLbNOX, the NAD+/NADH ratio, complex I-independent OCR, and ATP levels increased more pronouncedly compared with the NR treatment group, accompanied by significantly reduced NADH levels. Discussion: The present study suggests that compared with repletion of NAD+ alone, the combination of this therapeutic modality with alleviation of NADH overload may amplify the treatment effect of restoring NAD+/NADH balance in m.3243A>G fibroblasts.
    Keywords:  NADH; complex I; m.3243 A>G; mitoLbNOX; mitochondrial disease; nr
    DOI:  https://doi.org/10.3389/fphys.2023.1164287
  5. Cell Metab. 2023 Aug 22. pii: S1550-4131(23)00289-9. [Epub ahead of print]
    Preserved respiratory chain capacity and physiology in mice with profoundly reduced levels of mitochondrial respirasomes.
    Dusanka Milenkovic, Jelena Misic, Johannes F Hevler, Thibaut Molinié, Injae Chung, Ilian Atanassov, Xinping Li, Roberta Filograna, Andrea Mesaros, Arnaud Mourier, Albert J R Heck, Judy Hirst, Nils-Göran Larsson.
      The mammalian respiratory chain complexes I, III2, and IV (CI, CIII2, and CIV) are critical for cellular bioenergetics and form a stable assembly, the respirasome (CI-CIII2-CIV), that is biochemically and structurally well documented. The role of the respirasome in bioenergetics and the regulation of metabolism is subject to intense debate and is difficult to study because the individual respiratory chain complexes coexist together with high levels of respirasomes. To critically investigate the in vivo role of the respirasome, we generated homozygous knockin mice that have normal levels of respiratory chain complexes but profoundly decreased levels of respirasomes. Surprisingly, the mutant mice are healthy, with preserved respiratory chain capacity and normal exercise performance. Our findings show that high levels of respirasomes are dispensable for maintaining bioenergetics and physiology in mice but raise questions about their alternate functions, such as those relating to the regulation of protein stability and prevention of age-associated protein aggregation.
    Keywords:  OXPHOS; mitochondria; mitochondrial respirasomes; supercomplexes
    DOI:  https://doi.org/10.1016/j.cmet.2023.07.015
  6. J Cell Sci. 2023 Sep 01. pii: jcs260857. [Epub ahead of print]136(17):
    Mitochondrial phospholipid metabolism in health and disease.
    Alaumy Joshi, Travis H Richard, Vishal M Gohil.
      Studies of rare human genetic disorders of mitochondrial phospholipid metabolism have highlighted the crucial role that membrane phospholipids play in mitochondrial bioenergetics and human health. The phospholipid composition of mitochondrial membranes is highly conserved from yeast to humans, with each class of phospholipid performing a specific function in the assembly and activity of various mitochondrial membrane proteins, including the oxidative phosphorylation complexes. Recent studies have uncovered novel roles of cardiolipin and phosphatidylethanolamine, two crucial mitochondrial phospholipids, in organismal physiology. Studies on inter-organellar and intramitochondrial phospholipid transport have significantly advanced our understanding of the mechanisms that maintain mitochondrial phospholipid homeostasis. Here, we discuss these recent advances in the function and transport of mitochondrial phospholipids while describing their biochemical and biophysical properties and biosynthetic pathways. Additionally, we highlight the roles of mitochondrial phospholipids in human health by describing the various genetic diseases caused by disruptions in their biosynthesis and discuss advances in therapeutic strategies for Barth syndrome, the best-studied disorder of mitochondrial phospholipid metabolism.
    Keywords:  Barth syndrome; Cardiolipin; Membranes; Mitochondria; Phosphatidylethanolamine; Phospholipids
    DOI:  https://doi.org/10.1242/jcs.260857
  7. Proc Natl Acad Sci U S A. 2023 Sep 05. 120(36): e2302360120
    Impaired age-associated mitochondrial translation is mitigated by exercise and PGC-1α.
    Laura M de Smalen, Anastasiya Börsch, Aurel B Leuchtmann, Jonathan F Gill, Danilo Ritz, Mihaela Zavolan, Christoph Handschin.
      Sarcopenia, the age-related loss of skeletal muscle mass and function, can dramatically impinge on quality of life and mortality. While mitochondrial dysfunction and imbalanced proteostasis are recognized as hallmarks of sarcopenia, the regulatory and functional link between these processes is underappreciated and unresolved. We therefore investigated how mitochondrial proteostasis, a crucial process that coordinates the expression of nuclear- and mitochondrial-encoded mitochondrial proteins with supercomplex formation and respiratory activity, is affected in skeletal muscle aging. Intriguingly, a robust mitochondrial translation impairment was observed in sarcopenic muscle, which is regulated by the peroxisome proliferator-activated receptor γ coactivator 1 α (PGC-1α) with the estrogen-related receptor α (ERRα). Exercise, a potent inducer of PGC-1α activity, rectifies age-related reduction in mitochondrial translation, in conjunction with quality control pathways. These results highlight the importance of mitochondrial proteostasis in muscle aging, and elucidate regulatory interactions that underlie the powerful benefits of physical activity in this context.
    Keywords:  aging; mitochondria; proteostasis; sarcopenia; skeletal muscle
    DOI:  https://doi.org/10.1073/pnas.2302360120
  8. Life Sci Alliance. 2023 Nov;pii: e202302271. [Epub ahead of print]6(11):
    T cell differentiation drives the negative selection of pathogenic mitochondrial DNA variants.
    Imogen G Franklin, Paul Milne, Jordan Childs, Róisín M Boggan, Isabel Barrow, Conor Lawless, Gráinne S Gorman, Yi Shiau Ng, Matthew Collin, Oliver M Russell, Sarah J Pickett.
      Pathogenic mitochondrial DNA (mtDNA) single-nucleotide variants are a common cause of adult mitochondrial disease. Levels of some variants decrease with age in blood. Given differing division rates, longevity, and energetic requirements within haematopoietic lineages, we hypothesised that cell-type-specific metabolic requirements drive this decline. We coupled cell-sorting with mtDNA sequencing to investigate mtDNA variant levels within progenitor, myeloid, and lymphoid lineages from 26 individuals harbouring one of two pathogenic mtDNA variants (m.3243A>G and m.8344A>G). For both variants, cells of the T cell lineage show an enhanced decline. High-throughput single-cell analysis revealed that decline is driven by increasing proportions of cells that have cleared the variant, following a hierarchy that follows the current orthodoxy of T cell differentiation and maturation. Furthermore, patients with pathogenic mtDNA variants have a lower proportion of T cells than controls, indicating a key role for mitochondrial function in T cell homeostasis. This work identifies the ability of T cell subtypes to selectively purify their mitochondrial genomes, and identifies pathogenic mtDNA variants as a new means to track blood cell differentiation status.
    DOI:  https://doi.org/10.26508/lsa.202302271
  9. J Neuromuscul Dis. 2023 Aug 25.
    Resistance Exercise Training Rescues Mitochondrial Dysfunction in Skeletal Muscle of Patients with Myotonic Dystrophy Type 1.
    Valeria Di Leo, Conor Lawless, Marie-Pier Roussel, Tiago B Gomes, Gráinne S Gorman, Oliver M Russell, Helen A L Tuppen, Elise Duchesne, Amy E Vincent.
       BACKGROUND: Myotonic dystrophy type 1 (DM1) is a dominant autosomal neuromuscular disorder caused by the inheritance of a CTG triplet repeat expansion in the Dystrophia Myotonica Protein Kinase (DMPK) gene. At present, no cure currently exists for DM1 disease.
    OBJECTIVE: This study investigates the effects of 12-week resistance exercise training on mitochondrial oxidative phosphorylation in skeletal muscle in a cohort of DM1 patients (n = 11, men) in comparison to control muscle with normal oxidative phosphorylation.
    METHODS: Immunofluorescence was used to assess protein levels of key respiratory chain subunits of complex I (CI) and complex IV (CIV), and markers of mitochondrial mass and cell membrane in individual myofibres sampled from muscle biopsies. Using control's skeletal muscle fibers population, we classified each patient's fibers as having normal, low or high levels of CI and CIV and compared the proportions of fibers before and after exercise training. The significance of changes observed between pre- and post-exercise within patients was estimated using a permutation test.
    RESULTS: At baseline, DM1 patients present with significantly decreased mitochondrial mass, and isolated or combined CI and CIV deficiency. After resistance exercise training, in most patients a significant increase in mitochondrial mass was observed, and all patients showed a significant increase in CI and/or CIV protein levels. Moreover, improvements in mitochondrial mass were correlated with the one-repetition maximum strength evaluation.
    CONCLUSIONS: Remarkably, 12-week resistance exercise training is sufficient to partially rescue mitochondrial dysfunction in DM1 patients, suggesting that the response to exercise is in part be due to changes in mitochondria.
    Keywords:  Myotonic dystrophy type 1; mitochondrial dysfunction; myotonic dystrophy type 1 therapy; oxidative phosphorylation deficiency; resistance exercise training; skeletal muscle; strength training
    DOI:  https://doi.org/10.3233/JND-230099
  10. Proc Natl Acad Sci U S A. 2023 Sep 05. 120(36): e2302490120
    AMPK-FOXO-IP3R signaling pathway mediates neurological and developmental defects caused by mitochondrial DNA mutations.
    Hu Zhang, Yunan Zhu, Yuji Suehiro, Shohei Mitani, Ding Xue.
      Pathological mutations in human mitochondrial genomes (mtDNA) can cause a series of neurological, behavioral, and developmental defects, but the underlying molecular mechanisms are poorly understood. We show here that the energy-sensing adenosine monophosphate (AMP)-activated protein kinase (AMPK) signaling pathway plays a key role in mediating similar defects caused by different mtDNA mutations in Caenorhabditis elegans, including loss or reduction of osmotic, chemical and olfactory sensing, locomotion, and associative learning and memory, as well as increased embryonic lethality. mtDNA mutations cause reduced ATP (adenosine triphosphate) levels, activation of C. elegans AMPK AAK-2, and nuclear translocation of the FOXO transcription factor DAF-16. Activated DAF-16 up-regulates the expression of inositol triphosphate receptor ITR-1, an endoplasmic reticulum calcium channel, leading to increased basal cytosolic Ca2+ levels, decreased neuronal responsiveness, compromised synapses, and increased embryonic death. Treatment of mtDNA mutants with vitamin MK-4 restores cellular ATP and cytosolic Ca2+ levels, improves synaptic development, and suppresses sensory and behavioral defects and embryonic death. Our study provides crucial mechanistic insights into neuronal and developmental defects caused by mtDNA mutations and will improve understanding and treatment of related mitochondrial diseases.
    Keywords:  AMP-activated protein kinase; Caenorhabditis elegans; calcium homeostasis; mitochondrial genome mutations; neurological and developmental defects
    DOI:  https://doi.org/10.1073/pnas.2302490120
  11. Ann Clin Transl Neurol. 2023 Aug 29.
    Expanding the spectrum of neonatal-onset AIFM1-associated disorders.
    Alberto A Zambon, Daniele Ghezzi, Cristina Baldoli, Gianni Cutillo, Katia Fontana, Valentina Sofia, Maria Grazia Patricelli, Alessia Nasca, Stefano Vinci, Ivana Spiga, Eleonora Lamantea, Giovanna F Fanelli, Maria Grazia Natali Sora, Rosanna Rovelli, Antonella Poloniato, Paola Carrera, Massimo Filippi, Graziano Barera.
       OBJECTIVES: Pathogenic variants in AIFM1 have been associated with a wide spectrum of disorders, spanning from CMT4X to mitochondrial encephalopathy. Here we present a novel phenotype and review the existing literature on AIFM1-related disorders.
    METHODS: We performed EEG recordings, brain MRI and MR Spectroscopy, metabolic screening, echocardiogram, clinical exome sequencing (CES) and family study. Effects of the variant were established on cultured fibroblasts from skin punch biopsy.
    RESULTS: The patient presented with drug-resistant, electro-clinical, multifocal seizures 6 h after birth. Brain MRI revealed prominent brain swelling of both hemispheres and widespread signal alteration in large part of the cortex and of the thalami, with sparing of the basal nuclei. CES analysis revealed the likely pathogenic variant c.5T>C; p.(Phe2Ser) in the AIFM1 gene. The affected amino acid residue is located in the mitochondrial targeting sequence. Functional studies on cultured fibroblast showed a clear reduction in AIFM1 protein amount and defective activities of respiratory chain complexes I, III and IV. No evidence of protein mislocalization or accumulation of precursor protein was observed. Riboflavin, Coenzyme Q10 and thiamine supplementation was therefore given. At 6 months of age, the patient exhibited microcephaly but did not experience any further deterioration. He is still fed orally and there is no evidence of muscle weakness or atrophy.
    INTERPRETATION: This is the first AIFM1 case associated with neonatal seizures and diffuse white matter involvement with relative sparing of basal ganglia, in the absence of clinical signs suggestive of myopathy or motor neuron disease.
    DOI:  https://doi.org/10.1002/acn3.51876
  12. Front Cell Dev Biol. 2023 ;11 1215626
    Mitochondrial DNA mutations can influence the post-implantation development of human mosaic embryos.
    Akifumi Ijuin, Hiroe Ueno, Tomonari Hayama, Shunsuke Miyai, Ai Miyakoshi, Haru Hamada, Sumiko Sueyoshi, Shiori Tochihara, Marina Saito, Haruka Hamanoue, Teppei Takeshima, Yasushi Yumura, Etsuko Miyagi, Hiroki Kurahashi, Hideya Sakakibara, Mariko Murase.
      Introduction: Several healthy euploid births have been reported following the transfer of mosaic embryos, including both euploid and aneuploid blastomeres. This has been attributed to a reduced number of aneuploid cells, as previously reported in mice, but remains poorly explored in humans. We hypothesized that mitochondrial function, one of the most critical factors for embryonic development, can influence human post-implantation embryonic development, including a decrease of aneuploid cells in mosaic embryos. Methods: To clarify the role of mitochondrial function, we biopsied multiple parts of each human embryo and observed the remaining embryos under in vitro culture as a model of post-implantation development (n = 27 embryos). Karyotyping, whole mitochondrial DNA (mtDNA) sequencing, and mtDNA copy number assays were performed on all pre- and post-culture samples. Results: The ratio of euploid embryos was significantly enhanced during in vitro culture, whereas the ratio of mosaic embryos was significantly reduced. Furthermore, post-culture euploid and culturable embryos had significantly few mtDNA mutations, although mtDNA copy numbers did not differ. Discussion: Our results indicate that aneuploid cells decrease in human embryos post-implantation, and mtDNA mutations might induce low mitochondrial function and influence the development of post-implantation embryos with not only aneuploidy but also euploidy. Analyzing the whole mtDNA mutation number may be a novel method for selecting a better mosaic embryo for transfer.
    Keywords:  aneuploid cell decrease; mitochondria; mitochondrial DNA mutation; mosaic embryo; post-implantation development
    DOI:  https://doi.org/10.3389/fcell.2023.1215626
  13. Biochem Soc Trans. 2023 Aug 29. pii: BST20230012. [Epub ahead of print]
    Beyond the TCA cycle: new insights into mitochondrial calcium regulation of oxidative phosphorylation.
    Sandra H Lee, Hannah E Duron, Dipayan Chaudhuri.
      While mitochondria oxidative phosphorylation is broadly regulated, the impact of mitochondrial Ca2+ on substrate flux under both physiological and pathological conditions is increasingly being recognized. Under physiologic conditions, mitochondrial Ca2+ enters through the mitochondrial Ca2+ uniporter and boosts ATP production. However, maintaining Ca2+ homeostasis is crucial as too little Ca2+ inhibits adaptation to stress and Ca2+ overload can trigger cell death. In this review, we discuss new insights obtained over the past several years expanding the relationship between mitochondrial Ca2+ and oxidative phosphorylation, with most data obtained from heart, liver, or skeletal muscle. Two new themes are emerging. First, beyond boosting ATP synthesis, Ca2+ appears to be a critical determinant of fuel substrate choice between glucose and fatty acids. Second, Ca2+ exerts local effects on the electron transport chain indirectly, not via traditional allosteric mechanisms. These depend critically on the transporters involved, such as the uniporter or the Na+-Ca2+ exchanger. Alteration of these new relationships during disease can be either compensatory or harmful and suggest that targeting mitochondrial Ca2+ may be of therapeutic benefit during diseases featuring impairments in oxidative phosphorylation.
    Keywords:  MCU; NCLX; electron transport chain; mitochondrial dysfunction; mitochondrial permeability transition pores; oxidative phosphorylation
    DOI:  https://doi.org/10.1042/BST20230012
  14. Nat Metab. 2023 Aug 31.
    A defect in mitochondrial fatty acid synthesis impairs iron metabolism and causes elevated ceramide levels.
    Undiagnosed Diseases Network
      In most eukaryotic cells, fatty acid synthesis (FAS) occurs in the cytoplasm and in mitochondria. However, the relative contribution of mitochondrial FAS (mtFAS) to the cellular lipidome is not well defined. Here we show that loss of function of Drosophila mitochondrial enoyl coenzyme A reductase (Mecr), which is the enzyme required for the last step of mtFAS, causes lethality, while neuronal loss of Mecr leads to progressive neurodegeneration. We observe a defect in Fe-S cluster biogenesis and increased iron levels in flies lacking mecr, leading to elevated ceramide levels. Reducing the levels of either iron or ceramide suppresses the neurodegenerative phenotypes, indicating an interplay between ceramide and iron metabolism. Mutations in human MECR cause pediatric-onset neurodegeneration, and we show that human-derived fibroblasts display similar elevated ceramide levels and impaired iron homeostasis. In summary, this study identifies a role of mecr/MECR in ceramide and iron metabolism, providing a mechanistic link between mtFAS and neurodegeneration.
    DOI:  https://doi.org/10.1038/s42255-023-00873-0
  15. Cureus. 2023 Jul;15(7): e42550
    Urolithin A as a Potential Agent for Prevention of Age-Related Disease: A Scoping Review.
    Breanne Kothe, Sarah Klein, Stephanie N Petrosky.
      The aging of an organism is hallmarked by systemic loss of functional tissue, resulting in increased fragility and eventual development of age-related neurodegenerative, musculoskeletal, cardiovascular, and neoplastic diseases. Growing scientific evidence points to mitochondrial dysfunction as a key contributor in the aging process and subsequent development of age-related pathologies. Under normal physiologic conditions, the body removes dysfunctional mitochondria via an autophagic process known as mitophagy. Urolithin A (UA), a metabolite produced when gut microflora digests the polyphenol compounds ellagitannin and ellagic acid, is a known inducer of mitophagy via several identified mechanisms of action. The primary objective of this scoping review is to identify and summarize the clinical relevance of UA supplementation in the prevention of age-related pathology and diseases. A computer-assisted literature review was performed using PubMed and EMBASE for primary source research articles examining UA supplementation and aging-related pathologies. A total of 293 articles were initially identified from a database search, and 15 articles remained for inclusion in this review, based on predetermined criteria. Analysis of the 15 identified publications demonstrated that UA holds potential as a dietary intervention for slowing the progression of aging and preventing the development of age-related disease. This review also illustrates the potential role that mitochondrial health and inflammation play in the progression of age-related pathology. Identifying the clinical relevance of UA supplementation in the prevention of age-related pathology and diseases will help further the focus of research on treatments that may improve the longevity and quality of life in patients at risk for these comorbidities.
    Keywords:  age-related disease; aging; cholangiocarcinoma; colorectal cancer; neoplastic disease; neurodegenerative disease; osteoporosis; photo-aging; sarcopenia; urolithin a
    DOI:  https://doi.org/10.7759/cureus.42550
  16. Nat Rev Drug Discov. 2023 Sep 01.
    AAV-based in vivo gene therapy for neurological disorders.
    Qinglan Ling, Jessica A Herstine, Allison Bradbury, Steven J Gray.
      Recent advancements in gene supplementation therapy are expanding the options for the treatment of neurological disorders. Among the available delivery vehicles, adeno-associated virus (AAV) is often the favoured vector. However, the results have been variable, with some trials dramatically altering the course of disease whereas others have shown negligible efficacy or even unforeseen toxicity. Unlike traditional drug development with small molecules, therapeutic profiles of AAV gene therapies are dependent on both the AAV capsid and the therapeutic transgene. In this rapidly evolving field, numerous clinical trials of gene supplementation for neurological disorders are ongoing. Knowledge is growing about factors that impact the translation of preclinical studies to humans, including the administration route, timing of treatment, immune responses and limitations of available model systems. The field is also developing potential solutions to mitigate adverse effects, including AAV capsid engineering and designs to regulate transgene expression. At the same time, preclinical research is addressing new frontiers of gene supplementation for neurological disorders, with a focus on mitochondrial and neurodevelopmental disorders. In this Review, we describe the current state of AAV-mediated neurological gene supplementation therapy, including critical factors for optimizing the safety and efficacy of treatments, as well as unmet needs in this field.
    DOI:  https://doi.org/10.1038/s41573-023-00766-7
  17. Nature. 2023 Sep;621(7977): 47-48
    Previously unknown pathway for lipid biosynthesis discovered.
    Jean E Schaffer.
      
    Keywords:  Biochemistry; Cell biology; Metabolism
    DOI:  https://doi.org/10.1038/d41586-023-02502-y
  18. Cell. 2023 Aug 31. pii: S0092-8674(23)00854-1. [Epub ahead of print]186(18): 3983-4002.e26
    Phage-assisted evolution and protein engineering yield compact, efficient prime editors.
    Jordan L Doman, Smriti Pandey, Monica E Neugebauer, Meirui An, Jessie R Davis, Peyton B Randolph, Amber McElroy, Xin D Gao, Aditya Raguram, Michelle F Richter, Kelcee A Everette, Samagya Banskota, Kathryn Tian, Y Allen Tao, Jakub Tolar, Mark J Osborn, David R Liu.
      Prime editing enables a wide variety of precise genome edits in living cells. Here we use protein evolution and engineering to generate prime editors with reduced size and improved efficiency. Using phage-assisted evolution, we improved editing efficiencies of compact reverse transcriptases by up to 22-fold and generated prime editors that are 516-810 base pairs smaller than the current-generation editor PEmax. We discovered that different reverse transcriptases specialize in different types of edits and used this insight to generate reverse transcriptases that outperform PEmax and PEmaxΔRNaseH, the truncated editor used in dual-AAV delivery systems. Finally, we generated Cas9 domains that improve prime editing. These resulting editors (PE6a-g) enhance therapeutically relevant editing in patient-derived fibroblasts and primary human T-cells. PE6 variants also enable longer insertions to be installed in vivo following dual-AAV delivery, achieving 40% loxP insertion in the cortex of the murine brain, a 24-fold improvement compared to previous state-of-the-art prime editors.
    Keywords:  CRISPR-Cas9; directed evolution; genome editing; guide RNAs; pegRNAs; phage-assisted continuous evolution; prime editing; protein engineering
    DOI:  https://doi.org/10.1016/j.cell.2023.07.039
  19. Mol Ther Nucleic Acids. 2023 Sep 12. 33 572-586
    Targeting Duchenne muscular dystrophy by skipping DMD exon 45 with base editors.
    Michael Gapinske, Jackson Winter, Devyani Swami, Lauren Gapinske, Wendy S Woods, Shraddha Shirguppe, Angelo Miskalis, Anna Busza, Dana Joulani, Collin J Kao, Kurt Kostan, Anne Bigot, Rashid Bashir, Pablo Perez-Pinera.
      Duchenne muscular dystrophy is an X-linked monogenic disease caused by mutations in the dystrophin gene (DMD) characterized by progressive muscle weakness, leading to loss of ambulation and decreased life expectancy. Since the current standard of care for Duchenne muscular dystrophy is to merely treat symptoms, there is a dire need for treatment modalities that can correct the underlying genetic mutations. While several gene replacement therapies are being explored in clinical trials, one emerging approach that can directly correct mutations in genomic DNA is base editing. We have recently developed CRISPR-SKIP, a base editing strategy to induce permanent exon skipping by introducing C > T or A > G mutations at splice acceptors in genomic DNA, which can be used therapeutically to recover dystrophin expression when a genomic deletion leads to an out-of-frame DMD transcript. We now demonstrate that CRISPR-SKIP can be adapted to correct some forms of Duchenne muscular dystrophy by disrupting the splice acceptor in human DMD exon 45 with high efficiency, which enables open reading frame recovery and restoration of dystrophin expression. We also demonstrate that AAV-delivered split-intein base editors edit the splice acceptor of DMD exon 45 in cultured human cells and in vivo, highlighting the therapeutic potential of this strategy.
    Keywords:  AAV; CRISPR-Cas9; Duchenne muscular dystrophy; MT: RNA/DNA editing; adenine base editing; cytidine base editing; exon skipping; gene editing
    DOI:  https://doi.org/10.1016/j.omtn.2023.07.029
  20. Neurol Clin Pract. 2023 Oct;13(5): e200180
    Friedreich's Ataxia-Health Index: Development and Validation of a Novel Disease-Specific Patient-Reported Outcome Measure.
    Jamison Seabury, Spencer Rosero, Anika Varma, Jennifer Weinstein, Charlotte Engebrecht, Nuran Dilek, John Heatwole, Danae Alexandrou, Brittany Cohen, Jane Larkindale, David R Lynch, Courtney Park, Sub H Subramony, Ellen Wagner, Susan Walther, McKenzie Wells, Christine Zizzi, Chad Heatwole.
       Background and Objectives: To develop a valid, disease-specific, patient-reported outcome (PRO) measure for adolescents and adults with Friedreich ataxia (FA) for use in therapeutic trials.
    Methods: We conducted semistructured qualitative interviews and a national cross-sectional study of individuals with FA to determine the most prevalent and burdensome symptoms and symptomatic themes to this population. These symptoms and symptomatic themes were included as questions in the first version of the Friedreich's Ataxia-Health Index (FA-HI). We subsequently used factor analysis, beta interviews with 17 individuals with FA, and test-retest reliability assessments with 20 individuals with FA to evaluate, refine, and optimize the FA-HI. Finally, we determined the capability of the FA-HI to differentiate between subgroups of FA participants with varying levels of disease severity.
    Results: Participants with FA identified 18 symptomatic themes of importance to be included as subscales in the FA-HI. The FA-HI demonstrates high internal consistency and test-retest reliability, and it was identified by participants as highly relevant, comprehensive, and easy to complete. FA-HI total and subscale scores statistically differentiated between subgroups of participants with varying levels of disease burden.
    Discussion: Initial evaluation of the FA-HI supports its validity and reliability as a PRO for assessing how individuals with FA feel and function.
    DOI:  https://doi.org/10.1212/CPJ.0000000000200180
  21. Orphanet J Rare Dis. 2023 Aug 31. 18(1): 257
    Patient and caregiver experiences with pantothenate kinase-associated neurodegeneration (PKAN): results from a patient community survey.
    Thomas Klopstock, Saadet Mercimek-Andrews, Agnieszka Jurecka, Patricia Wood, Maciej Cwyl, Angelika Klucken, Antonio López, Roberta Scalise, Andrea Valle, Fatemeh Mollet, Belen Perez-Duenas, Marta Skowronska, Magdalena Chroscinska-Krawczyk, Maria Luisa Escolar, Anna Wade, David Rintell.
       BACKGROUND: Pantothenate kinase-associated neurodegeneration (PKAN) is a rare autosomal recessive genetic disorder of PANK2, which enables mitochondrial synthesis of coenzyme A. Its loss causes neurodegeneration with iron accumulation primarily in motor-related brain areas. Symptoms include dystonia, parkinsonism, and other disabilities. PKAN has been categorized as classic PKAN, with an age of onset ≤ 10 years, rapid progression, and early disability or death; and atypical PKAN, with later onset, slower progression, generally milder, and more diverse symptom manifestations. Available treatments are mostly palliative. Information on the lived experience of patients with PKAN and their caregivers or on community-level disease burden is limited. It is necessary to engage patients as partners to expand our understanding and improve clinical outcomes. This patient-oriented research study used multiple-choice and free-form question surveys distributed by patient organizations to collect information on the manifestations and disease burden of PKAN. It also assessed respondents' experiences and preferences with clinical research to inform future clinical trials.
    RESULTS: The analysis included 166 surveys. Most respondents (87%) were parents of a patient with PKAN and 7% were patients, with 80% from Europe and North America. The study cohort included 85 patients with classic PKAN (mean ± SD age of onset 4.4 ± 2.79 years), 65 with atypical PKAN (13.8 ± 4.79 years), and 16 identified as "not sure". Respondents reported gait disturbances and dystonia most often in both groups, with 44% unable to walk. The classic PKAN group reported more speech, swallowing, and visual difficulties and more severe motor problems than the atypical PKAN group. Dystonia and speech/swallowing difficulties were reported as the most challenging symptoms. Most respondents reported using multiple medications, primarily anticonvulsants and antiparkinsonian drugs, and about half had participated in a clinical research study. Study participants reported the most difficulties with the physical exertion associated with imaging assessments and travel to assessment sites.
    CONCLUSIONS: The survey results support the dichotomy between classic and atypical PKAN that extends beyond the age of onset. Inclusion of patients as clinical research partners shows promise as a pathway to improving clinical trials and providing more efficacious PKAN therapies.
    Keywords:  Atypical PKAN; Classic PKAN; Clinical outcomes assessment; Dystonia; Hallervorden–Spatz syndrome; Iron accumulation; NBIA; Neurodegeneration; PANK2; Patient-oriented
    DOI:  https://doi.org/10.1186/s13023-023-02869-1
  22. Mov Disord Clin Pract. 2023 Aug;10(Suppl 3): S41-S44
    Ataxia due to a COQ8A Novel Variant in Primary Coenzyme Q10 Deficiency.
    Gerardo Chavira-Hernández, Carlos Eduardo Piña-Avilés, Carlos Zúñiga-Ramírez.
      
    Keywords:  COQ8A; ataxia; coenzyme Q10; movement disorders
    DOI:  https://doi.org/10.1002/mdc3.13781
  23. Genetics. 2023 Aug 31. pii: iyad159. [Epub ahead of print]
    Cornelia de Lange Syndrome mutations in SMC1A cause cohesion defects in yeast.
    Jingrong Chen, Erin N Floyd, Dean S Dawson, Susannah Rankin.
      Cornelia de Lange Syndrome (CdLS) is a developmental disorder characterized by limb truncations, craniofacial abnormalities, and cognitive delays. CdLS is caused mainly by mutations in genes encoding subunits or regulators of the cohesin complex. Cohesin plays two distinct roles in chromosome dynamics: it promotes looping, organization, and compaction of individual chromosomes, it holds newly replicated sister chromatids together until cell division. CdLS-associated mutations result in altered gene expression likely by affecting chromosome architecture. Whether CdLS mutations cause phenotypes through impact on sister chromatid cohesion is less clear. Here we show that CdLS-associated mutations introduced into the SMC1A gene of budding yeast had measurable impacts on sister chromatid cohesion, mitotic progression, and DNA damage sensitivity. These data suggest that sister chromatid cohesion-related defects may contribute to phenotypes seen in CdLS affected individuals.
    Keywords:  Cohesinopathy; SMC1; cell cycle; chromosome segregation; disease alleles
    DOI:  https://doi.org/10.1093/genetics/iyad159
  24. Nat Med. 2023 Aug 31.
    Boosting the efficacy of emergency contraception.
    Karen O'Leary.
      
    Keywords:  Clinical trials; Public health; Reproductive biology
    DOI:  https://doi.org/10.1038/d41591-023-00077-9
  25. Nat Rev Neurol. 2023 Aug 29.
    The translational potential of cholesterol-based therapies for neurological disease.
    Marta Valenza, Giulia Birolini, Elena Cattaneo.
      Cholesterol is an important metabolite and membrane component and is enriched in the brain owing to its role in neuronal maturation and function. In the adult brain, cholesterol is produced locally, predominantly by astrocytes. When cholesterol has been used, recycled and catabolized, the derivatives are excreted across the blood-brain barrier. Abnormalities in any of these steps can lead to neurological dysfunction. Here, we examine how precise interactions between cholesterol production and its use and catabolism in neurons ensures cholesterol homeostasis to support brain function. As an example of a neurological disease associated with cholesterol dyshomeostasis, we summarize evidence from animal models of Huntington disease (HD), which demonstrate a marked reduction in cholesterol biosynthesis with clinically relevant consequences for synaptic activity and cognition. In addition, we examine the relationship between cholesterol loss in the brain and cognitive decline in ageing. We then present emerging therapeutic strategies to restore cholesterol homeostasis, focusing on evidence from HD mouse models.
    DOI:  https://doi.org/10.1038/s41582-023-00864-5
  26. Cell. 2023 Aug 21. pii: S0092-8674(23)00862-0. [Epub ahead of print]
    PINK1, Keap1, and Rtnl1 regulate selective clearance of endoplasmic reticulum during development.
    Ruoxi Wang, Tina M Fortier, Fei Chai, Guangyan Miao, James L Shen, Lucas J Restrepo, Jeromy J DiGiacomo, Panagiotis D Velentzas, Eric H Baehrecke.
      Selective clearance of organelles, including endoplasmic reticulum (ER) and mitochondria, by autophagy plays an important role in cell health. Here, we describe a developmentally programmed selective ER clearance by autophagy. We show that Parkinson's disease-associated PINK1, as well as Atl, Rtnl1, and Trp1 receptors, regulate ER clearance by autophagy. The E3 ubiquitin ligase Parkin functions downstream of PINK1 and is required for mitochondrial clearance while having the opposite function in ER clearance. By contrast, Keap1 and the E3 ubiquitin ligase Cullin3 function downstream of PINK1 to regulate ER clearance by influencing Rtnl1 and Atl. PINK1 regulates a change in Keap1 localization and Keap1-dependent ubiquitylation of the ER-phagy receptor Rtnl1 to facilitate ER clearance. Thus, PINK1 regulates the selective clearance of ER and mitochondria by influencing the balance of Keap1- and Parkin-dependent ubiquitylation of substrates that determine which organelle is removed by autophagy.
    Keywords:  Drosophila; ER-phagy; Keap1; PINK1; Parkin; Rtnl1
    DOI:  https://doi.org/10.1016/j.cell.2023.08.008
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